Sensing a threat in Pennsylvania’s U.S. Senate race, Donald Trump issued a warning Thursday that surging Republican candidate Kathy Barnette would upend the GOP’s chances of holding the seat in November and urged voters to back his pick, celebrity heart surgeon Mehmet Oz. The former president’s statement echoed growing panic among his allies and Barnette’s rivals over her sudden and unforeseen rise ahead of the state’s Tuesday primary. Trump adding, Barnette “will never be able to win” in a general election matchup against Democrats and that Oz “is the only one” who can defeat the Democratic nominee.